1. Technical Field
Embodiments of semiconductor chips are fabricated with processes that include illuminating un-masked portions of a semiconductor wafer through a reticle during a photo-lithographic step.
2. Description of the Related Art
Electronic circuits, which are fabricated on semiconductor substrates, perform a variety of functions. Some examples are electronic circuits formed as amplifiers, filters, and/or power supplies. In some cases, many circuits are formed on a single semiconductor substrate to provide a multitude of functions. The end product of the fabrication is commonly called a semiconductor “chip” or integrated circuit.
The electronic circuits are often constructed on a semiconductor substrate. The substrate may initially be a single wafer, and after several electronic circuits are formed, the wafer is cut into many individual semiconductor chips. Later, each chip may be packaged in its own plastic or other suitable housing for use in an electronic system.
The process of semiconductor fabrication is expensive and time consuming. Thus, the quantity and quality of the integrated circuits is often very important for a high yield and good financial earnings. Another method is to make smaller circuits that use less area. A third method is to take steps to ensure that the chips which are made operate correctly. In order to maximize return on investment, manufacturers of semiconductor chips try to maximize the number of operational chips that can be formed on a single wafer. One method of maximizing the number of operational chips formed on a single wafer may be accomplished by using all of the available space on the wafer as efficiently as possible.
The number of operational chips that can be formed on the wafer may be affected by several factors. Using current technology, the semiconductor wafer may have a diameter of 6 inches, 8 inches, 12 inches or some other suitable size. In addition to the diameter of the wafer, the number of individual chips that can be formed from a single wafer may be limited by the type, size, complexity, and function of the electronic circuits that are fabricated.
In addition to the number of chips produced from a single wafer, the quality of the circuits formed on the chips also may affect the manufacturer's return on investment. Several factors may affect circuit quality. For example, in order to operate in an acceptable manner, some circuits require components having values that fall within narrow tolerance ranges. In cases where one or more components have values that are outside of an acceptable tolerance range, the entire circuit may not operate correctly, and thus the entire chip may have to be discarded. In other cases, even when the electronic circuits operate, the operational characteristics may not fall within the desired specifications. In these cases, when one or more components have values that fall outside pre-defined tolerance ranges, the chip may be less valuable. Thus, an improvement in quality of circuits formed on the chip will increase the return on investment for the manufacturer.